Date of Observation: 12/16/2022
Name: Zach Guy
Zone: Northwest Mountains
Route Description: Anthracite Range, Schuylkill Ridge, Axtell. Submitted via text or morning bino tours.
Observed avalanche activity: Yes
Avalanches: See photos and details below. Failures sometime in the past few days.
The weekly snowpack summary is here. While some areas in the Northwest Mountains received more than a few inches of new snow, the main story this week was clear skies, cold temps, and consistent wind transport and pressing. Accompanying this wind loading were some impressive natural avalanches and a lingering wind slab problem as we move into the weekend.
Date of Observation: 12/16/2022
Name: Zach Guy
Zone: Northwest Mountains
Route Description: Viewed from Mt. Baldy
Observed avalanche activity: Yes
Avalanches: Adding more avalanches to the previous observation. Ruby, Afley, Peeler Peak, Treasury, and Gothic. The Gothic slide may have run today, the others ran sometime in the past 4 days.
Date of Observation: 12/16/2022
Name: Zach Guy
Zone: Northwest Mountains
Route Description: Mt. Baldy, traveling primarily on south and southeast aspects to 12,400′
Observed avalanche activity: Yes
Avalanches: A handful of destructive persistent slabs ran in the past few days. Most notable includes a pair of very large hard slabs (D3) on Purple Ridge that ran over Purple Bench and reached the Slate River, ~2100 vertical, and several others in the ~D2-D3 range off or Ruby Peak, Peeler Peak, Schuylkill Peak, Bichmond, and Gothic. All fit the same distribution pattern as previous cycles. Today’s observed slides were all on W to N to E starting near or above treeline. Hard to say exactly which days they ran on, some crowns looked very fresh (24-36 hours), others were more drifted in and probably ran during the peak of the last storm (~12/13)
Weather: Cold, clear, light northerly winds this afternoon on Baldy. I could see notable transport in the Southeast Mountains this morning, especially near Whiterock.
Snowpack: Apart from one collapse in a relatively thin area (from wind erosion), we saw no signs of instability under foot. Test results on a windloaded SE facing slope near treeline produced propagating results (PST 47/137 END) under a 130 cm hard slab (up to pencil hard). The weak layer is showing substantial improvements compared to the start of the month; It was 4F+ and rounding. Still an ugly structure and now scary consequences, but on an improving trend.
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Date of Observation: 12/15/2022
Name: Evan Ross
Zone: Southeast Mountains
Route Description: Mt Emmons. N to E. 9,000ft to 11,400ft.
Observed avalanche activity: Yes
Avalanches: Lots of old avalanche activity in the terrain, but nothing new or notable that doesn’t fit the mold.
Weather: Mostly cloudy, calm wind, cold.
Snowpack: Climbing up through the terrain the snowpack transitioned from weak and shallow, to deep and stubborn. Somewhere in the middle, there was a narrow band where the persistent slab avalanche problem may have been reactive. Only a few collapse with notable effort. A couple of those shook trees but didn’t produce on the nearby steep slopes. Overall the snowpack structure remains poor and has just become less reactive or stubborn.
9,600ft. NE aspect, 35-degree slope. HS 60cm. ECTN. The mid-pack slab was 4F over the F November Facets. Facets are developing throughout this snowpack and the mid-pack slab was losing its ability to propagate a collapse. Near this pit, I found some recently formed wind drifts that added structure and made that specific snowpack reactive.
11,000ft. ENE aspect, 30-degree slope. HS 100cm. ECTX, CT21 SC on the November facets. Here the mid-pack slab was 1F .8mm rounded grains over the F 2.5mm faceted grains. Poor snowpack structure. No amount of jumping or punching ski boots to the weak layer was producing a collapse.
Somewhere between those two locations, it felt like there should be a sweet spot where the persistent slab avalanche problem would be more reactive. I couldn’t put my finger on where exactly that is.
11,200ft. NNE aspect. This slope had previously avalanched. Below the bed surface, there was about 10cm of well-developed facets. Above the bed surface, there was 25 to 30cm of new snow that was faceting and losing strength.
Photos:
Date of Observation: 12/14/2022
Name: Evan Ross Zach Kinler
Zone: Northwest Mountains
Route Description: Slate River Valley. NE 9,000-10,800.
Observed avalanche activity: Yes
Avalanches: A recent large avalanche in the Climax Chutes that likely ran last night. At 10am the crown was blown back in while the avalanche debris looked fresh. This was a cross-loaded terrain feature below 10,800ft.
Weather: Cold. Generally, calm wind except for a few gusts down in the open valley. Mostly cloudy. A few flakes, but no real accumulation.
Snowpack: Obvious signs of instability were rare. A few collapses with notable effort and a couple of localized shooting cracks.
HS varied between about 90cm to 135cm on average. We targeted two test profiles on NE aspects, one with an HS of 90cm at 10,000ft and one with an HS of 125cm at 10,700ft. In both locations the snowpack structure was poor. Thick slabs to 1F or P, over F to F+ November Facets. The change in grain size at the interface was about 1.5mm. ECT results were ECTP22 in the lower location and ECTX at the upper location where it took several full-strength whacks after the standard test to get through the slab and produce a failure.
Photos:
Date of Observation: 12/14/2022
Name: Billy Barr
Zone: Southeast Mountains
Route Description: Gothic townsite
Observed avalanche activity: No
Weather: Little weather here with just a trace of snow each of the past 2 days but no warming as yesterday’s high ws 14F and today’s low 10 with a steady wind bringing more blowing snow. No sign of sun and snowpack down to 23½”.
The 12.2-12.9 Weekly Snowpack Summary is here. Two storm cycles kickstarted widespread natural avalanching. The week ended with high pressure moving in and excellent riding on lower angled terrain.
